Update editor width is chars when soft wrap is toggled

Closes #858

spec/editor-spec.coffee

@@ -1039,10 +1039,12 @@ describe "Editor", ->
     describe "when the text exceeds the editor width and the scroll-view is horizontally scrolled", ->
       it "wraps the text and renders properly", ->
         editor.attachToDom(heightInLines: 30, widthInChars: 30)
+        editor.setWidthInChars(100)
         editor.setText("Fashion axe umami jean shorts retro hashtag carles mumblecore. Photo booth skateboard Austin gentrify occupy ethical. Food truck gastropub keffiyeh, squid deep v pinterest literally sustainable salvia scenester messenger bag. Neutra messenger bag flexitarian four loko, shoreditch VHS pop-up tumblr seitan synth master cleanse. Marfa selvage ugh, raw denim authentic try-hard mcsweeney's trust fund fashion axe actually polaroid viral sriracha. Banh mi marfa plaid single-origin coffee. Pickled mumblecore lomo ugh bespoke.")
         editor.scrollLeft(editor.charWidth * 30)
         editor.trigger "editor:toggle-soft-wrap"
         expect(editor.scrollLeft()).toBe 0
+        expect(editor.activeEditSession.getSoftWrapColumn()).not.toBe 100
 
   describe "text rendering", ->
     describe "when all lines in the buffer are visible on screen", ->

src/editor.coffee

@@ -929,6 +929,7 @@ class Editor extends View
 
   # Toggle soft wrap on the edit session.
   toggleSoftWrap: ->
+    @setWidthInChars()
     @activeEditSession.setSoftWrap(not @activeEditSession.getSoftWrap())
 
   calculateWidthInChars: ->